1. Field of the Invention
The present invention relates to methods and devices for controllably handling relatively large flanged pipe and fittings. More particularly, the present invention relates to a novel method and apparatus for supporting a blind pipe flange or manway cover during removal and replacement procedures.
2. Description of the Related Art
Numerous industrial vessels and structures such as tanks, drums and process towers are constructed with one or more large portals for the ingress and egress of maintenance personnel or equipment. Often, such portals are often characterized as “manways”. The manway structure integral with the tank, drum or tower typically comprises a short length of 18″ to 36″, for example, steel pipe having one axial end welded to a structural wall of the tank, drum or tower, The opposite end of such a stub pipe length is fitted with a bolt flange which comprises a steel ring welded around the pipe perimeter. The ring has a radially projecting face surface that is transversely perforated by bolt holes distributed uniformly around the ring circumference.
The opening into the tank, drum or tower interior through the interior bore of the integrally attached stub pipe is the manway passage. Due to the fact that the very purpose of the tank, drum or tower is to confine a process environment, often under extreme temperature and/or pressure conditions, it is essential for the manway opening to be sealed during tank, drum or tower usage.
Frequently, if not usually, such manway portals are covered or closed by a steel, plate-like article having a perforated periphery to accommodate a plurality of clamping bolts distributed around the plate periphery. Some industries characterize such a manway portal cover as a “blind flange”. The clamping bolts extend between the outside face of the cover plate and the backside face of the ring flange that is secured to the manway defining stub pipe to uniformly clamp the contiguous inner faces of the flange and plate against a sealing gasket.
It is not unusual for such a manway to be projected from the sheer, vertical face of a high pressure process tower at an elevation of 100 ft. or greater above the ground. To compound matters, due to a high operating pressure within the tower, the manway cover may be several inches thick. Consequently, the manway cover weight is several hundred pounds. Clearly, some form of mechanical assistance is required to remove and replace such a manway cover.
Mobile lifts and cranes are often used to support a manway cover during a removal or replacement process. However, restricted accessibility may prohibit the use of such machines in some cases. The prior art has suggested and utilized numerous attachments and fixtures secured to the tank, drum or tower to attach a suitable lifting device such a pulley, chain hoist or come-a-long. However, any permanently attached fixture is exposed to the elements and/or the immediate industrial atmosphere. Not infrequently, the industrial atmosphere is considerably more corrosive than the natural elements. Accordingly, the structural integrity and reliability of a permanently exposed structure deteriorates rapidly.
Although the prior art has proposed and produced numerous portable and temporary hoist hangers for the purpose of safely handling a heavy manway cover, few of the portable devices have found their way into the workplace. There may be many reasons for this result but foremost, such prior art devices are nearly as heavy as the manway cover to be supported and they are clumsy and time consuming to attach.
It is, therefore, an objective of the present invention to provide an implement and method of use for supporting a hoisting mechanism from a pipe flange.
Also an object of the present invention is a relatively small and light apparatus for attaching a hoist hanger eye to a pipe connecting flange.
Another object of the present invention is a method and apparatus for securing a structural appliance to one flange ring of a 2-ring joint without separating the rings or opening the joint.